Early attempts were unsuccessfully made to synthesize-.alpha.-amino acids or derivatives thereof by reacting a Schiff base or a nitrile with carbon monoxide and hydrogen. [Bull. Chem. Soc. Japan 33 (160) 78]
U.S. Pat. No. 3,766,266 to Wakamatsu discloses a method of producing an N-acyl-.alpha.-amino acid which comprises holding an aldehyde, an amide of a carboxylic acid and carbon monoxide at a temperature of 10.degree. C. to 300.degree. C. and a pressure of at least 500 atm. in the presence of a carbonylation catalyst until said N-acyl-.alpha.-amino acid is formed.
In Chem. Comm. 1540 (1971), Wakamatsu, et al. disclose a cobalt-catalyzed reaction which gives various N-acyl amino-acids from an aldehyde, an amide and carbon monoxide. In this disclosure, while benzaldehyde was used as the starting aldehyde, there was no corresponding .alpha.-phenyl-substituted amino acid obtained. Instead of the expected amino acid product, an imine was obtained by a simple "amination" reaction.
An article by Parnaud, et al., in Journal of Molecular Catalysis, 6 (1979) 341-350, discusses the synthesis potential and the catalytic mechanism for the reaction wherein N-acyl-.alpha.-amino acids are produced by reacting an aldehyde, CO and an amide in the presence of dicobalt octacarbonyl.
In amidocarbonylation, the aldehyde can be generated in situ from allyl alcohol, alkyl halides, oxiranes, alcohols and olefins followed by the reaction with an amide and carbon monoxide to produce an N-acyl-.alpha.-amino acid.
A related Patent, U.S. Pat. No. 3,996,288 discloses that when an alcohol or certain of its ester derivatives is held at 50.degree. C. to 200.degree. C. and 10 to 500 atm. in the presence of hydrogen, carbon monoxide, the amide of a carboxylic acid and a carbonylation catalyst, an aldehyde having one more carbon atom than the alcohol or ester is formed in good yield. If the amide has at least one active hydrogen atom on its amide nitrogen, it further reacts with the aldehyde and carbon monoxide to form an N-acylamino acid.
Hirai, et al. discuss a process for combining the transition metal catalyzed isomerization of allyl alcohol to aldehyde and cobalt catalyzed amidocarbonylation to provide a route from allylic alcohols to N-acyl-.alpha.-amino acids. See Tetrahedron Letters, Vol. 23, No. 24, pp. 2491-2494, 1982.
U.S. Pat. No. 4,264,515 by R. Stern et al. discloses a process for obtaining terminal N-acyl-.alpha.-amino acids by a reaction catalyzed by a cobalt carbonylation catalyst wherein the aldehyde is produced in situ from olefins and CO/H.sub.2 mixtures An unsaturated vegetable oil or C.sub.8 -C.sub.30 monoolefinic compound is reacted with an amide, carbon monoxide and hydrogen in the presence of a cobalt catalyst. The process is operated in one step and provides for increased selectivity.
Cobalt and rhodium catalysts have been used in the past for synthesis of amido acids.
In Applicant's copending application, Ser. No. 06/720,248, now abandoned, it was found that the use of a combined HRh(CO)PPh.sub.3)-Co.sub.2 (CO).sub.8 catalyst afforded more stability to the dicobalt octacarbonyl catalyst and allowed the reaction to proceed at a lower temperature and pressure than with dicobalt octacarbonyl alone.
Murata, et al. disclose the results of research wherein methylacrylate was hydroformylated in the presence of a Co.sub.2 (CO).sub.8 catalyst and a phosphine ligand. It was found that the various di(tertiary phosphine) ligands had distinct effects on activity. It is disclosed that previously the general conclusion in the art was that the addition of a phosphorous ligand to the hydroformylation catalyst would decrease the rate.
In this study, it was found that HCo(CO).sub.2 (P-P) is responsible for an increase in activity and, although attempts to isolate it were unsuccessful it was found that:
(1) The treatment of Co.sub.2 (CO).sub.8 with trialkylphosphine (PR.sub.3) under the hydroformylation reaction conditions leads to the formation of HCo(CO).sub.3 (PR.sub.3) and
(2) Apparently diphos acts as a bidentate ligand.
See Bull. Chem. Soc. Jpn. 53, 214-218 (1980) Co.sub.2 (CO).sub.8 -di(tertiary phosphine) complex for methyl acrylate reaction.
In New Synthesis With Carbon Monoxide, 1980, p. 53, Falbe discusses the characteristic features of ligand-modified cobalt catalysts. Features listed include:
(1) Increased stability of oxo catalysts.
(2) Reduced activity necessitating greater reactor volumes.
(3) Marked hydrogenation activity resulting in only alcohols and no aldehydes with about 15% of the olefin feed hydrogenated to paraffins.
(4) High n:iso product ratio. There is a discussion of cobalt catalysts in hydroformylation in JOMC 1985, 283 No. 1-3, p. 226. In this study it was found that the chelate complex HCo(CO).sub.2 (Bu.sub.2 PCH.sub.2 CH.sub.2 PBu.sub.2) was found to be inactive as a catalyst for the hydroformylation of propene at 180.degree. C. It was slowly transformed, however, under the reaction conditions into an active form.
The instant invention relies on a cobalt catalyst promoted by a bidentate phosphine ligand for the synthesis of N-acetylamino acids or alkyl N-acetylamino acids from alpha olefins or internal olefins, acetamide and syngas wherein yields of N-acetylamino acids are as high as 80% and the recovery of cobalt catalyst is as high as 85-100%. The presence of the ligand increases both reaction rate and cobalt catalyst stability. The reaction requires higher reaction temperatures and regioselectivity levels are lower. The products of internal olefins can be used as surface active agents, specialty surfactants and oil additives. The N-acetylamino acid products of the alpha olefins can be used as surfactants. The amido acid products of allyl acetate are useful in polyamide-ester synthesis.